Drinking water standards are established for contaminants which may have adverse effects on people’s health and for contaminates which have aesthetic effects such as taste, odor and staining. Drinking water standards are usually established through Maximum Contamination Levels (MCL). The MCL is the maximum level of contaminant allowed in a water system. It is usually expressed in:
Milligrams per liter (mg/L) = parts per million (ppm)
Micrograms per liter (μg/L) = parts per billion (ppb)
More info on New York Sate limits can be found here:
New York State Department of Health – Residential Well Fact Sheet
Coliform Bacteria: (MCL: Total absence or Less than 1.0)
This test evaluates for coliform bacteria, which is widely distributed in the environment and E.coli which is found in the feces of warm blooded animals. The presence of coliform is indicative of contamination. All water systems should be free of total coliform and E.coli to be considered safe. Therefore the presence of any coliform is cause for concern and corrective actions should be taken. Chlorine bleach or ultra violet light disinfection is recommended.
Alkalinity: (MCL: No designated limit)
Primarily a function of carbonate, bicarbonate and hydroxide, alkalinity measures the acid neutralizing capacity of water. Alkalinity has a major importance in connection with the corrosion control of water.
Chloride: (MCL: 250mg/L)
Chloride is suspected of being a contributor to high blood pressure. High concentrations may contribute to the deterioration of domestic plumbing and water heaters. Water can become contaminated by natural salt deposits, highway road salt and water softeners. Reverse osmosis is the recommended treatment.
Chlorine: (MCL: 4.0 mg/L)
Chlorine is a common disinfectant used in water treatment. Some people who drink water containing chlorine well in excess of the MCL could experience some stomach discomfort.
Conductivity: (Normal range 50-1500 μMHOs/CM)
Conductivity measure the degree of mineralization of water. The conductivity value is used in the determination of corrosivity.
Copper: (MCL: 1.3 mg/L)
A common source of contamination is copper piping. Corrosive water will cause leaching. High levels may impart a bitter taste to the water. Treat by neutralizing corrosive water
Corrosivity: (Normal range is –1 to +1)
Corrosivity is a complex characteristic of the relationship between pH, alkalinity, calcium hardness, temperature and total dissolved solids or conductivity. A value lower than -1 indicates corrosive water. Corrosive water can gradually weaken and destroy household piping and leach metals such as lead, copper, and iron into tap water. Water with a value of higher than +1 may be prone to scaling and calcium buildup. Treat by neutralization.
Fluoride: (MCL: 4 mg/L)
Fluoride is a naturally occurring compound found in rocks. Some of these compounds, dissolve easily into groundwater as it flows through gaps between the rocks. Most water supplies contain some naturally occurring fluoride. Fluoride is also voluntarily added to some drinking water systems as a public health measure for reducing the incidence of cavities among the treated population. Whether to add Fluoride to water supplies is decided by the local municipality.
Hardness: (0-60 mg/L soft water, 61-120 mg/L moderately hard, 121-180 mg/L hard water)
Hardness measures the amount of dissolved calcium and magnesium carbonates. Very hard water increase soap consumption. And may precipitate in appliances and pipes reducing their capacity. Hardness has no adverse health effects. Treat with a water softener.
Hydrogen Sulfide: (MCL: No designated limit)
Hydrogen Sulfide is a gas. It is easily identifiable by a “rotten egg” odor. Hydrogen sulfide may be produced during the decay of iron bacteria. Treat with oxidation and filtration.
Iron: (MCL: 0.3 mg/L)
Iron occurs naturally in many groundwater supplies. High levels may cause red or brown staining to fixtures and laundry or impart a metallic taste. Treat by neutralizing corrosive water with an iron filter
Lead: (MCL: 0.015 mg/L)
Lead exposure can cause serious health effects. Water may be contaminated from rocks and soil, lead pipes lead in solder, water pump fittings, discarded lead batteries, landfills and hazardous waste sites.
Manganese: (NYS MCL: 0.3 mg/L / EPA MCL: 0.05 mg/L)
Manganese occurs naturally in many groundwater supplies. High levels may cause black or gray discoloration to plumbing fixtures and laundry or impair the taste of coffee and tea. Treat by neutralizing corrosive water or with an iron filter. The allowable limit set by the State of New York is 0.3 mg/L. The limit set by the EPA is more strict at 0.05 mg/L
Nitrate: (MCL: 10 mg/L)
Nitrite: (MCL: 1 mg/L)
Many commercial fertilizers contain nitrogen in the form of nitrates. Excess nitrate can leach into the ground and contaminate water supplies. Within the digestive system, nitrate is converted into very toxic nitrite and can interfere with the oxygen carrying capacity of the blood. Pregnant women and infants should not consume water with nitrate or nitrite above the MCL to avoid methemoglobinemia or blue baby syndrome. Treat with reverse osmosis or ion exchange.
pH: (Normal range is 6.5 to 8.5)
The term pH indicates whether water is acidic or basic. The scale is from 0 to 14, with 7.0 being neutral. Low pH values tent to increase corrosivity making many substances such as metals and hardness minerals more soluble.
Sodium: (MCL: No designated limit)
Sodium occurs naturally in almost all groundwater. Excessive sodium intake increases the risk of hypertension. Concentration of less than 20mg/L are recommended for sodium restricted individuals. Most waters containing high levels of sodium are due to water softeners containing sodium chloride. Home water softeners add significant sodium to the water because they exchange sodium for the hardness minerals, The recommended treatment is reverse osmosis or a potassium chloride softener.
Total Dissolved Solids: (MCL: 500 mg/L)
Total Dissolved Solids (TDS) is a measure of all dissolved inorganic material in water. Excess TDS may impart a mineral taste and have possible health effects. The TDS value is used in the determination of corrosivity.
Turbidity: (MCL: 5 NTU)
Turbidity is a measure of the clarity of the water and measures how much the water scatters light passing through it. Common sources of turbidity come from sediment in the water from silt and clay. Excessive turbidity can interfere with UV disinfection.